Euromir '95: First results from the Dustwatch-P detectors of the European space exposure facility

Abstract A small, passive, retrievable dust detector/collector experiment (Dustwatch-P), based on thin foil and aerogel capture cells has been developed at the University of Kent by the Unit for Space Sciences & Astrophysics (USSA). It was mounted in the European Space Exposure Facility (ESEF) designed by the Institut d'Astrophysique Spatial (Orsay, France) and flown on the joint ESA/Russian Space Agency EuroMir '95 mission. The experiment sampled micrometeoroids and space debris in the immediate vicinity of a large space facility (Mir) and offers the opportunity for detailed particle characterisation by intact capture. Dustwatch-P was housed in 2 ESEF cassettes, each contained: 1849mm 2 of aluminium foil capture cells, 2.4μm and 5μm thick respectively, mounted above a pure copper plate; 8450mm 2 of 12mm thick silica aerogel (density of 0.1g/cm 3 and pore size of approximately 0.07μm). 8650mm 2 of experiment-holder surfaces (highly polished 6061-T6 aluminium alloy) were also used for detection. The foils and experiment-holder surfaces readily give a flux measurement for comparison to previous data with chemical classification of any impactor residues. The aerogel was intended to capture, with minimal modification, incident hypervelocity particles. Dustwatch-P was exposed to the space environment when the ESEF cassettes were opened during Mir EVA's on the 20/21 October '95. The cassettes were hermetically sealed in space for return to Earth in February '96. We present the first results of post-flight analysis. A hypervelocity perforation has been found in each foil and a region of ejecta impacts indicating a large impact in the vicinity. This impact rate gives a higher flux than expected, possibly due to a debris cloud.